Did not consider this. Intermodulation and other distortion by-products are going to be difficult to control although I have no experience with the performance

Did not consider this. Intermodulation and other distortion by-products are going to be difficult to control although I have no experience with the performance of modern amps for sub-MHz frequency ranges. Building a working prototype that can beam ~1W (or even 100mW) a few feet would be very interesting and would do a lot to lessen my skepticism.